Vacuum trucks are used for excavation, whenever there are buried objects which might be damaged by mechanical excavation equipment. For example, one would not want to use mechanical excavation equipment to unearth a buried natural gas pipeline.
Vacuum trucks use a stream of fluids, usually air or water, to dislodge earth. A vacuum is then used to draw water with solids from the excavation into a holding tank.
U.S. Pat. No. 5,996,171 (Bowers from 1999) teaches some novel solids handling features on a vacuum truck which uses air. The Bowers reference teaches the use of filters and separators to separate solids from the air. The Bowers reference also teaches the use of a holding tank which is capable of being dumped. As an alternative to dumping, the Bowers reference teaches the use of removable holding tanks. This enables the holding tank to be removed and taken to a dumping site by a transport vehicle, while the vacuum truck continues to operate using a replacement holding tank. Another patent reference which teaches solids separation include U.S. Pat. No. 5,295,317 (Perrott from 1994). Another patent reference which teaches the use of a holding tank which can be dumped is U.S. Pat. No. 6,752,467 (Palrose et al from 2004).